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ACTIVE AND SEMI-PASSIVE LIME TREATMENT OF ACID MINE DRAINAGE AT LEVIATHAN MINE, CALIFORNIA BULLETIN
Citation:
TETRA TECH EM INC. ACTIVE AND SEMI-PASSIVE LIME TREATMENT OF ACID MINE DRAINAGE AT LEVIATHAN MINE, CALIFORNIA BULLETIN. EPA/540/S-05/015, 2006.
Impact/Purpose:
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Description:
As part of the Superfund Innovative Technology Evaluation (SITE) program, U.S. Environmental Protection Agency (EPA) National Risk Management Research Laboratory (NRMRL), in cooperation with EPA Region IX, the state of California, and the Atlantic Richfield Company (ARCO) evaluated lime treatment of acid mine drainage (AMD) and acid rock drainage (ARD) at the Leviathan Mine Superfund site located in Alpine County, California. EPA evaluated two lime treatment systems in operation at the mine in 2002 and 2003: an active lime treatment system operated in biphasic and monophasic modes, and a semi-passive alkaline lagoon treatment system. The treatment systems utilize the same chemistry to treat AMD generated within the mine workings and ARD generated from surface seeps within waste rock; the addition of lime to neutralize acidity and remove toxic levels of metals by precipitation. The primary metals of concern in the AMD and ARD include aluminum. arsenic, copper, iron, and nickel; secondary water quality indicator metals include cadmium, chromium, lead, selenium. and zinc.
The technology evaluation occurred between June 2002 and October 2003, during the operation of both the active lime treatment system (in biphasic and monophasic modes) and the semi-passive alkaline lagoon treatment system. The evaluation consisted of multiple sampling events of each treatment system during 6 months of operation separated by winter shutdown. Throughout the evaluations, EPA collected metals data on each system's influent and effluent streams, documented metals removal and reduction in acidity within each system's unit operations, and recorded operational information pertinent to the evaluation of each treatment system. EPA evaluated the treatment systems independently, based on removal efficiencies for primary and secondary target metals, comparison of effluent concentrations to discharge standards mandated by EPA in 2002, and on the characteristics of resulting metals-laden solid wastes. Removal efficiencies of individual unit operations were also evaluated.
Both treatment systems were shown to be extremely effective at neutralizing acidity and reducing the concentrations of the 10 target metals in the AMD and ARD flows at Leviathan Mine to below EPA discharge standards. Although the influent concentrations for the primary target metals were up to 3,000 fold above the EPA discharge standards, both lime treatment systems were successful in reducing the concentrations of the primary target metals in the AMD and ARD to between 4 and 20 fold below EPA discharge standards. In general, removal efficiencies for the five primary target metals exceeded 95 percent. In addition, the active lime treatment system operated in biphasic mode was shown to be very effective at separating arsenic from the AMD prior to precipitation of other metals, subsequently reducing the total volume of hazardous solid waste produced by the treatment system. Separating the arsenic into a smaller solid waste stream significantly reduces materials handling and disposal costs.
Based on the success of lime treatment at the Leviathan Mine site, the state of California will continue to treat AMD at the site using the active lime treatment system in biphasic mode and ARCO will continue to treat ARD using the semi-passive alkaline lagoon treatment system.